1. Field of the Invention
The present invention relates to an image processing apparatus having an analog/digital converter (hereinafter, referred to as xe2x80x9cADCxe2x80x9d), and more particularly, to an image processing apparatus having an ADC capable of securing a dynamic range for the levels of input analog YUV or RGB signals when converting the input analog YUV or RGB signals into digital YUV or RGB signals. The present application is based on Korean Application No. 2001-33244, filed Jun. 13, 2001, which is incorporated herein by reference.
2. Description of the Related Art
Image processing apparatuses having an ADC include TV, DVD, PC, and the like. These image processing apparatuses convert analog YUV or RGB signals into digital YUV or RGB signals using the ADC and process an image signal using the digital YUV or RGB signals. For example, in order to convert input analog YUV or RGB signals into a desired format, the input analog YUV or RGB signals are first converted into the digital YUV or RGB signal using an ADC and then the digital YUV or RGB signal are converted into a desired format.
However, the levels of the input analog YUV or RGB signals vary depending on image processing apparatuses. Thus, the levels of the input analog YUV or RGB signals may exceed the dynamic range in the ADC. In this case, the ADC cannot process all of the levels of the input analog YUV or RGB signals. In other words, a saturation phenomenon occurs in the ADC. Then, a screen is not normally displayed. The levels of the input YUV or RGB signals may be much lower than the standard signal level, which may be processed by the ADC. In this case, the quality of the screen is deteriorated.
Accordingly, in the prior art, a method of using an ADC with wide headroom is proposed to secure the dynamic range in the ADC for analog YUV or RGB signals having a wide variable width in each of the image processing apparatuses. However, the ADC obtains a digital signal, which deteriorates bit resolution compared to the original signal if the levels of the input YUV or RGB signals are too much lower than the standard signal level, which is processed by the ADC.
To solve the above-described problems, it is an object of the present invention to provide an image processing apparatus for inputting analog YUV or RGB signals, which are controlled to automatically control a gain and have uniform levels of synchronous signals, into an ADC so that the dynamic range in the ADC is optimized.
Accordingly, to achieve the above object, there is provided an image processing apparatus having an analog/digital converter (ADC) for converting input analog luminance and chrominance signals into digital luminance and chrominance signals. The image processing apparatus includes an automatic gain control signal generating means, an automatic gain control amplifier, and a plurality of automatic gain control amplifiers. The automatic gain control signal generating means generates an automatic gain control signal, which controls the levels of the analog luminance and chrominance signals, using the level of a synchronous signal detected from a digital Y luminance signal output from the ADC. The automatic gain control amplifier amplifies the level of an analog Y luminance signal by a predetermined value using the automatic gain control signal generated in the automatic gain control signal generator and transmits the amplified level of the analog Y luminance signal to the ADC. The plurality of automatic gain control amplifiers amplify the levels of analog UV chrominance signals corresponding to the analog Y luminance signal by predetermined values using the automatic gain control signal generated in the automatic gain control signal generator and transmit the amplified levels of analog UV chrominance signals to the ADC.
It is preferable that the automatic gain control amplifier amplifies the level of a synchronous signal contained in the analog Y luminance signal by a predetermined value, and the plurality of automatic gain control amplifiers amplify the levels of synchronous signals contained in the analog UV chrominance signals by predetermined values.
To achieve the above object, there is provided an image processing apparatus having an ADC for converting input analog RGB color signals into digital RGB color signals. The image processing apparatus includes an automatic gain control signal generator, an automatic gain control amplifier, and a plurality of automatic gain control amplifiers. The automatic gain control signal generator generates an automatic gain control signal, which controls the levels of the analog RGB color signals using the level of a synchronous signal detected from a first color signal of the digital RGB color signals. The automatic gain control amplifier amplifies the analog level of the first color signal by a predetermined value using the automatic gain control signal generated in the automatic gain control signal generator and transmits the analog level of the first color signal to the ADC. The plurality of automatic gain control amplifiers amplify the levels of analog color signals corresponding to the first color signal by predetermined values using the automatic gain control signal generated in the automatic gain control signal generator and transmit the levels of the analog color signals to the ADC.